Microwave oscillators utilizing accumulating cavities are the subjects of the Kurokawa et al U.S. Pat. No. 3,628,171 and the Harp et al U.S. Pat. No. 3,931,587. My copending application Ser. No. 699,722 filed June 24, 1976 and now U.S. Pat. No. 4,034,314, teaches the use of auxiliary cavities for providing more stable operation and lower losses in such apparatus. The state of the prior art limits the output power of such devices due to the limited space available at the periphery of the accumulation cavity for mounting and coupling coaxial circuit mounted negative resistance diode oscillators. Further, the oscillators of the prior art utilize the center of the accumulator cavity for placement of a capacitively coupled output probe, thereby precluding this space from use for a tuning device or a coaxial circuit mounted diode or other active element.
A further encroachment on the available space which may be utilized for diode circuits is the space limiting effect of tuning devices which must extend into the accumulator side walls when the center of the cavity is pierced by an output probe. When sidewall tuning mechanisms are used, the effective tuning range is limited compared to systems using axial tuning mechanisms.
Still another shortcoming in prior art apparatus is the detrimental effect of the change in coupling coefficients of both output probe and input coupling circuits as a change is made in the frequency of operation of the system. The result is limiting in terms of constant power output capability over the tuning range of the system due to variation in power output with those coupling coefficient changes.